Suspected Islamist extremists have attacked a secondary school and military checkpoint in Nigeria's northeast, leaving 11 people dead including seven students, the military said Monday.

Details were sketchy and the information could not be independently confirmed. Mobile phone lines have been cut in much of the northeast since the start of a military offensive targeting Islamist extremist group Boko Haram on May 15 and access to the area is limited.

Nigeria's Boko Haram Islamists have stormed a neighborhood in the restive city of Maiduguri, killing at least 11 people with weapons hidden in a coffin, local residents said Monday.

There were conflicting reports as to the number of people who lost their lives in the attack that began late Friday.

Nigeria's military claimed on Thursday that U.S.-designated "global terrorist" Abubakar Adam Kambar was killed in an operation last year, though Washington had not confirmed the death.

Lieutenant Colonel Mohammed Suleiman said Kambar, believed to have links to al-Qaida's north African branch and Nigerian Islamist extremist group Boko Haram, was killed on March 18, 2012.

Nigeria has formally declared the Boko Haram Islamist sect and Ansaru, its suspected offshot, "terrorist" groups and issued a law to ban them, a presidential statement said on Tuesday.

"President Goodluck Jonathan has formally approved the proscription of Boko Haram and authorized the gazetting of an order declaring the group's activities illegal and acts of terrorism," said the statement from his office.

Nigeria's military said Friday it had released 58 women and children held in connection with the Islamist insurgency in the country's northeast under a peace gesture announced 10 days ago.

The youngest of the children released in Borno state told journalists at a ceremony announcing the move that he was nine years old. Twenty women and children were released in Borno, while 38 others in neighboring Yobe state.

Nigeria's military said Friday it had arrested 56 more Islamist insurgents as part of an ongoing offensive in the country's restive northeast, but provided few other details on the operation.

A military statement said they were arrested in various locations but did not specify where or when. It added that weapons seized included homemade bombs.

Nigerian lawmakers approved Thursday a bill to outlaw gay marriage and crack down on gay rights, including criminalizing public displays of affection between same-sex couples.

The House of Representatives unanimously approved the bill which provides for jail terms of up to 14 years for gay marriage.

Nigeria's security services said Thursday they had discovered a home in the northern city of Kano where Lebanese nationals had stored weapons intended to attack Israeli and Western targets in Nigeria.

The Kano state director for Nigeria's main intelligence branch, the Department of State Security (DSS), told journalists the compound's owner had ties to Hizbullah and that the home had harbored a Hizbullah "cell".

Nigeria's military on Thursday dismissed as "empty propaganda" claims by Boko Haram's leader that soldiers have retreated during an ongoing offensive, insisting the campaign has heavily damaged the Islamist insurgents.

In a video obtained by Agence France Presse on Tuesday, Boko Haram chief Abubakar Shekau said soldiers have at times "turned and ran" when facing Islamist fighters and rejected military boasting about the success of the operation.

The leader of Islamist extremist group Boko Haram claims in a video obtained by Agence France Presse on Tuesday that Nigerian soldiers have retreated during an ongoing military offensive while insurgents have sustained little damage.

The video marks the first public comments from Boko Haram leader Abubakar Shekau since the start of a sweeping offensive by the Nigerian army on May 15 and also includes a call for foreign Islamists to join the fight in Nigeria.